**Mesh Align Plus doesn't work on Blender 4.5 / 5.1**

[monpinero]

When you enable the addon it works, but when you disable it you get an error. After that you can't enable it again without restarting Blender.

Errors:

1. On disable: has no attribute 'unregister'
2. On re-enable: already registered as a subclass 'MAPLUS_OT_AlignPointsBase'

The fix is 3 small changes in the code:

1. __init__.py – add unregister to the import
2. utils/system.py – remove base classes from the registration list (Blender 4.x registers them automatically)
3. utils/system.py – add try/except in register() so it doesn't crash if a class is already in memory

Patched zip attached – tested and working on Blender 4.5 LTS and 5.1.

mesh_mesh_align_plus-FIXED-v2.zip

[monpinero]

Bug: Two errors when using Mesh Align Plus on Blender 4.5+ / 5.1

Blender versions tested: 4.5 LTS, 5.1

---

Error 1 – on disable:

AttributeError: module 'bl_ext.user_default.mesh_mesh_align_plus' has no attribute 'unregister'

Cause: __init__.py imports only register from utils/system.py but not unregister.

Fix in __init__.py:

# Before
from .utils.system import register

# After
from .utils.system import register, unregister

---

Error 2 – on re-enable after disable (without Blender restart):

register_class(...): already registered as a subclass 'MAPLUS_OT_AlignPointsBase'

Cause 1: All *Base classes are explicitly listed in the classes tuple in utils/system.py. In Blender 4.x+, registering a subclass automatically registers its base class too, so registering the base class explicitly causes a conflict.

Fix: Remove all *Base / *BaseClass entries from the classes tuple in utils/system.py.

Cause 2: If unregister() fails (see Error 1), classes remain registered in memory. On next enable, register() attempts to register them again.

Fix in utils/system.py:

def register():
    for cls in classes:
        try:
            bpy.utils.register_class(cls)
        except Exception:
            bpy.utils.unregister_class(cls)
            bpy.utils.register_class(cls)

---

[ericsnekbytes]

Thank you for looking at this! <3 I'll try to find the time to merge and release sometime soon. Will keep you posted :D